Ethylene and propylene are important building blocks for the petrochemical industry. These olefins are used in the manufacturing of polymers such as polyethylene, polypropylene, polystyrene and many more chemicals of commercial interest. Over 90% of the global olefin production comes from the high temperature steam cracking of naphtha or ethane and propane. The steam cracking process, which utilizes furnaces, is highly energy intensive, and 1.5 to 2 tons of carbon dioxide is produced for every ton of olefin product.
Natural gas production from shale deposits has dramatically increased supply in recent years. As a result of the continued global demand for olefins and the potential for a new growing supply of ethane and propane available in natural gas liquids from shale deposits, a significant amount of interest and investment is currently centered around expanding the capacity of ethylene and propylene derived from these new sources. Numerous olefin grass root and expansion projects are either under contract or in the planning stages to take advantage of the relative low cost liquids from wet shale gas. However, there are many environmental and cost challenges to bringing on this level of new capacity.
Olefin production is the largest emitter of CO2 and NOx in the organic chemical industry. With worldwide ethylene production at ˜150 MT/yr, the industry emits 150-300 MT/yr of CO2 and roughly 1.4 MT/yr of NOx. Projects located in severe EPA non-attainment zones are challenged by the increase cost of NOx control. The total greenhouse gas (GHG) emission profile, reported in CO2 equivalents, is another critical part of the permitting for all production expansions.
The industry continues to push for production technology that: (1) generates higher overall yield of ethylene and propylene; (2) increases the run length between furnace turnarounds (e.g. inspections, repairs, improvements, etc.); (3) lowers steam and energy utilization; and (4) lowers all GHGs including carbon dioxide and NOx. ODH of ethane and propane offers a potential solution for these needs.
The ODH of ethane and propane to olefins offers a production route that can significantly reduce CO2 emissions and virtually eliminate NOx emissions from world scale plants. ODH is a selective catalytic process that produces primarily ethylene and water as products, and is thereby an exothermic reaction (reaction 1).CH3CH3+½O2→CH2CH2+H2O ΔHo=−105 kJ/mol  (1)                The per pass yield of the ODH reaction is not limited by thermodynamic equilibrium, as it is in pyrolysis, (reaction 2).CH3CH3+Heat⇄CH2CH2+H2 ΔHo=+137 kJ/mol  (2)        ODH provides an opportunity to achieve some of the objectives to improve the efficiency of olefin production. Therefore, there is a need for improved reactors and processes for facilitating efficient ODH conversions.        